1. Field of the Invention
The present invention relates to an apparatus and method for manufacturing an anisotropic formed body having anisotropy to exhibit in specific directions within a matrix various properties, such as electrical conductivity, heat conductivity, expansion coefficient, light transmittance, magnetism, hardness, elasticity, water absorption, dielectric constant, gas permeability, piezoelectric characteristics, and vibration absorption. In particular, the present invention relates to an apparatus and method for manufacturing an anisotropic formed body in which anisotropy is imparted by utilizing a magnetic field.
2. Description of the Related Art
As an example of an anisotropic formed body as mentioned above, an anisotropic conductive device is known. For example, an anisotropic conductive connector for electrical connection of a microphone and a printed circuit board contained in a mobile phone is known. As an example of such an anisotropic conductive connector, there is known a formed body composed of a disc-shaped main body portion with a continuous conductive portion formed therein. The main body portion uses electrically insulating silicone rubber as a matrix. Conductive, magnetic fine particles are oriented in a specific direction to form the continuous conductive portion. This formed body is generally obtained as follows: A mold with conductive fine particles arranged therein is filled with liquid silicone rubber, and the conductive fine particles are oriented by a parallel magnetic field generated by permanent magnets embedded in the upper and lower portions of the mold so as to be opposed to each other. Then, the silicone rubber is crosslinked.
As a prior-art technical document disclosing a technique in which an anisotropic formed body is formed by utilizing the parallel magnetic field of such permanent magnets, the applicant of the present invention has referred to the following patent document.
However, in the method of forming an anisotropic formed body by utilizing the magnetic field of permanent magnets, there are limitations regarding the intensity of the magnetic field that can be generated. Thus, the functional fine particles allowing orientation and exhibiting properties such as conductivity are restricted to ferromagnetic materials such as nickel or iron. With paramagnetic materials, such as aluminum, platinum, palladium, titanium, and manganese, and diamagnetic materials, such as gold, silver, copper, metal oxide, metal nitride, metal carbide, metal hydroxide, carbon, organicpolymer, protein, and DNA, it is difficult to effect orientation so as to attain the intended anisotropy. Further, due to its weak magnetic force and unevenness in magnetic field generated by its surface irregularities, it is rather difficult for a permanent magnet to generate a uniform parallel magnetic field in a large space. Thus, it is very difficult to produce an anisotropic formed body exhibiting an anisotropy which is parallel and of a uniform interval within a large area.